Brock Lesnar and his legal team are on the hunt for the culprit in his recent failed drug tests.

In a formal request to the Nevada State Athletic Commission acquired by MMAjunkie, Lesnar's attorney, Howard Jacobs, detailed their attempts to narrow down the source of the banned substances that caused the UFC heavyweight to commit two USADA violations this past July. The letter is dated Sept. 19.

Lesnar returned to MMA at UFC 200 after four-and-a-half years away from the sport. He defeated Mark Hunt by unanimous decision.

On Monday, the 39-year-old fighter was granted a continuance on his appeal hearing with the NSAC to allow more time to put together a case against the doping allegations. His team is pointing to Lesnar's use of eye medication and foot cream as a possible explanation for his test failures.

Lesnar's samples came back positive for clomiphene, an anti-estrogen agent that's been connected to steroid cycles due to its potential for increasing testosterone production, and clomiphene metabolites.

"We are still investigating this matter (which investigation includes the ongoing testing of products used by Mr. Lesnar prior to the date of the positive test)," Jacobs wrote. "To provide further detail, I am advised that the testing laboratory (Korva Labs) initially tested an eye medication, which was negative for either clomiphene or clomiphene metabolites.

"Subsequent testing has been conducted on a foot cream; that testing has included three separate extraction attempts, all of which have failed. A fourth extraction attempt is being made by Korva Labs this week."

According to Jacobs, they will not be able to confirm the presence of clomiphene in the foot cream until a successful extraction is accomplished.

Complicating the matter further is Lesnar's pre-fight medical questionnaire, a copy of which Erik Magraken of Combat Sports Law acquired. Magraken notes that Lesnar responded "no" in the section of the questionnaire that asks if the fighter took or received any medications or creams in the month prior to UFC 200.

In the next section regarding his use of nutritional supplements and vitamins, Lesnar only lists multivitamins, creatine, and protein powder.

Should Lesnar's appeal fail, he could face a suspension, the forfeiture of his UFC 200 purse, and a monetary fine, in addition to other sanctions. Though his rescheduled hearing does not have a date yet, the NSAC's next meeting takes place Nov. 10.